1. Field of the Invention
The present invention relates to metal purification and, more particularly, to means for removing nonmetallic inclusions and like foreign matter from metals and alloys.
2. Description of the Prior Art
Gas turbine engine components are subjected to severe conditions of service, for example, high temperatures, high stresses and corrosive atmospheres. As a result, it is desirable to fabricate such components from the cleanest available metals and alloys. It is especially important to utilize metals and alloys having minimum levels of nonmetallic inclusions, such as SiO.sub.2, Al.sub.2 O.sub.3, MgO, etc., which adversely affect the mechanical properties of the material. To this end, various techniques have been utilized in the past to insure metal cleanliness, for example, vacuum induction melting, vacuum arc remelting and electroslag remelting have been employed in converting alloys into ingots for forging, powder making and investment casting. However, these techniques have produced less than satisfactory results, in some cases increases in the incidence of foreign inclusion contamination actually being observed.